Solvent Effects on the Phosphorescence of Gold(III) Complexes Chelated by β-Multisubstituted Corroles

Abstract

A set of gold corrole complexes containing four different β-substituent groups (Br/I/CF3), namely, 4Br–Au, 4I–Au, and 4CF 3 –Au, were investigated; all showed room temperature phosphorescence. The phosphorescence quantum yields of the corroles were determined using tetraphenylporphyrin as a reference: Φph (4I–Au, 0.75%) > Φph (4Br–Au, 0.64%) > Φph (4CF 3 -Au, 0.38%). 4CF 3 –Au exhibited near-IR emission (858 nm, aerobic); absorbance intensity for the Q-band was higher than that for the Soret band. Complex 4I–Au showed a longer phosphorescence lifetime (82 μs) compared to those of 4Br–Au (53 μs) and 4CF 3 –Au (28 μs; N2, tol). Thermally activated delayed fluorescence (TADF) emission of 4I/Br–Au complexes was observed: stronger emission intensity correlated with increasing temperature. Good negative correlations for 4I/Br–Au were observed between the Soret band absorption energy and the solvent polarizability: excited states of 4I/Br–Au are more polar than their ground states. TD-DFT calculations revealed very fast intersystem crossing (ISC) rate constants, 2.20 × 1012 s–1 (4CF 3 –Au) > 1.96 × 1011 s–1 (4Br–Au) > 1.15 × 1011 s–1 (4I–Au), and importantly, the reverse intersystem crossing (rISC) rate constants are determined as 1.68 × 107 s–1 (4I–Au) > 2.40 × 103 s–1 (4Br–Au) ≫ 8.09 × 10–8 s–1 (4CF 3 –Au). The exceptionally low rISC rate constant of 4CF 3 –Au is attributed to its more steric and deformed structure bearing a larger energy gap between the S1 and T1 states.

NIR-emissive, singlet-oxygen-sensitizing gold tetra(thiocyano)corroles

“…A promising approach has recently been outlined by Gross who found fascinating variations of photophysical properties in 2,3,17,18-tetra-Br/I/CF 3 -substituted gold corroles. 18 Herein, we report a new class of Au corroles, [19][20][21][22][23][24][25][26][27][28][29][30][31][32] based on 2,3,17,18-tetrathiocyanocorrole ligands developed in one of our laboratories. 33 We accordingly describe two new complexes -2,3,17,18-tetra(thiocyano)-10-(4-bromophenyl)-5,15-bis(4-cyanophenyl)corrolato-Au(III), 1, and 2,3,17,18tetrathiocyano-10-(4,7-dimethoxynaphthalen-1-yl)-5,15-bis(4cyanophenyl)corrolato-Au(III), 2 (Scheme 1).…”

Orthogonal Design of Fe−N4 Active Sites and Hierarchical Porosity in Hydrazine Oxidation Electrocatalysts

“…The contracted and tri‐ (rather than di‐) anionic N 4 coordination core of corroles induces unusual reactivity and stability at the low and high oxidation state, respectively [40,41] . The redox potentials of metallocorroles are easily tuned by the nature of substituents at the meso ‐C position and via selective postfunctionalization [42,43] . Moreover, metallocorroles are extremely stable towards hydrolysis, and show a much reduced tendency of forming inactive μ‐oxo‐bridged bis‐iron complexes [44,45] …”

“…[40,41] The redox potentials of metallocorroles are easily tuned by the nature of substituents at the meso-C position and via selective postfunctionalization. [42,43] Moreover, metallocorroles are extremely stable towards hydrolysis, and show a much reduced tendency of forming inactive μ-oxo-bridged bis-iron complexes. [44,45] To achieve high power density in fuel cells, the FeÀ N 4 sites must be exposed to fast flow of reactants and electrons.…”

β-Bis-CF3-substituted phosphorus corroles, theory and experiments

“…6 CF 3 substitution, especially on the peripheral beta positions of the corrole macrocycle has been found to induce dramatic effects on the photophysical and redox properties of metallocorrole complexes; a wide assortment of products (M(Cor), M = P, Co, Au, Cu, Ga, Al) have been investigated. [8][9][10][11][12][13] Fully beta trifluoromethyl-substituted copper(III) and gold(III) corroles reported by the Ghosh group have also served to help allow for better understanding of how the CF 3 effect is manifested in the electronic structure of the corrole macrocyle. 14 Partial trifluoromethylation is also an interesting target; full CF 3 substitution for some certain metallocorroles appears to be currently unachievable synthetically.…”